CHAPTER V. 

 CIRCULATION OF THE BLOOD. 



I. STUDY OF THE CIRCULATION IN THE WEB OF THE 

 FROG'S FOOT. 



1. INJECT a few drops of a one-per-cent solution of curare in 

 the dorsal lymph sac of a frog. After fifteen minutes or a half 

 hour tie the frog, face down, upon the frog-board. Spread the 

 web, but not too tightly, over the opening in the board. Place the 

 board on the stage of the microscope so that the opening in the 

 board coincides with the opening of the stage. Study the circula- 

 tion in the web with the low power first. If the circulation in the 

 smaller vessels has stopped, the web is drawn too tight and must be 

 somewhat more relaxed. 



Note the direction of the flow from the larger vessels into the 

 smaller ones and from the smaller toward the larger. Can you 

 make out a pulsation in any of the vessels ? If so, in which ones ? 

 What is the direction of the flow in the pulsating vessels, from 

 large vessel into branches or from branches into large vessel? 

 What is the speed of flow in the large vessels as compared with the 

 smaller ones ? Can you make out the outlines of the corpuscles in 

 any of the vessels? Can you distinguish more than one kind of 

 corpuscle ? 



2. Examine now with a higher power, so that the corpuscles 

 may be distinctly seen. Select a small vessel where the flow is not 

 so rapid and note the position and speed of movement of the red 

 and white corpuscles in the Wood stream. 



As determined by the movement of the corpuscles, in what part 

 of the stream is the speed of flow greatest ? Explain. 



How do the red and white corpuscles compare in numbers ? 



[so] 



